Military talks between the rival Koreas have collapsed, a unification ministry official in Seoul said on Wednesday, dealing a setback to efforts to restart international aid-for-disarmament talks.

Tensions have eased on the divided peninsula since the start of the year, with both sides calling for dialogue, raising hopes the neighbours could rebuild relations shattered over the past two years by a series of deadly attacks and failed nuclear talks.

Colonels from the two Koreas, still technically at war since their 1950-53 civil conflict ended in a truce, not a treaty, talked for two days but failed to get past the first hurdle of the preliminary meeting -- setting the agenda for senior discussions.

The talks have collapsed; they haven't even agreed on a date for their next meeting, the official told Reuters, referring to the first meeting since the North's attack on the southern island of Yeonpyeong in November, which killed four people and raised the threat of possible all-out war.

The South's Defence Ministry said in a statement that the North's representatives had unilaterally walked out of the meeting room.

In Washington, Pentagon spokesman Colonel Dave Lapan called news of the walkout unfortunate and said the United States had actively encouraged dialogue between the two Koreas as a way to reduce tensions on the peninsula.

We are hopeful they can work out whatever differences there were and resume talks as soon as possible, Lapan said.

Seoul said the offer for senior-level military talks still stood, but on the condition the North takes responsible steps regarding last year's attacks, a ministry official said.

The talks also became bogged down over the procedural issue of what rank any senior talks would take, with the South demanding either a ministerial or four-star general confab while North insisted on vice-ministerial dialogue.

While the failed talks underline the deep divisions and distrust between the rivals, analysts said they were hardly surprised and that any talks would follow a stop-start pattern.

I thought it would take some time due to a gap in views of the both, said Park Syung-je, an expert at the Asia Strategy Institute. Next time ahead of talks, South Korea should check if North Korea truly wants them.

Tensions rose on the divided peninsula last year when 46 South Korean sailors were killed in an attack on a naval vessel. North Korea, which denies responsibility for that attack, also revealed major advances in its nuclear programme in November.

Beijing and Washington had set inter-Korean dialogue as a prerequisite to restart six-party talks which offer the North aid and diplomatic recognition in return for disabling its nuclear arms program. Tokyo and Moscow are the other six-party members.

The North has said it wants to return to the broader negotiations, but Seoul and Washington have questioned its sincerity about denuclearizing -- pointing to its revelations about a uranium-enrichment programme.

Without having the bilateral talks between the two Koreas, holding six-party talks also looks unclear now, said Kim Seung-hwan of the Centre for Strategic and International Studies.

The North quit the six-way talks in 2009, declaring the process dead, in protest against U.N. sanctions for conducting nuclear and missile tests.

The North's shelling of Yeonpyeong, the first attack against civilians on South Korean soil since the Korean War, set off a wave of war-like rhetoric that worried financial markets in a region home to one-sixth of the world's economy.

Under pressure from their main allies, the United States and China, the neighbours have stopped their combative language and reopened a hotline at their border.

And the two sides showed some signs of cooperation on Wednesday, with Seoul sending a telegram to Pyongyang saying it was ready to discuss humanitarian issues.

During the preliminary military talks this week, the South demanded the North acknowledge its role in shelling of Yeonpyeong and the attack on the vessel, the defence ministry said.

North Korea repeated that it was not responsible for the sinking the naval vessel and blamed the Yeonpyeong attack on the South's live-fire drills in disputed waters.

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